Vision and Central Visual Pathways

Question 1

Describe the pathway of the Optic Tract

Answer 1

Eye–> Optic Nerves (CN2) –> Optic Chiasm–> Optic Tract–> Hypothalamus, Lateral Geniculate Nucleus, Superior Colliculus, Striate Cortex

Question 2

Describe the vision and eye placement of prey animals.

Answer 2

Laterally placed eyes
Increased peripheral vision to see predators coming
Monocular vision- bad depth perception

Question 3

Which type of animal has more decussation? Predator or prey animals?

Answer 3

Prey animals have more decussation

Question 4

What 4 pathways do Optical nerves take after penetrating the optic disk?

Answer 4

The Retino-_____ pathways!

1. Geniculostriate
2. Pretectal
3. Tectal
4. Hypothalamic

Question 5

Which retinal pathway(s) are cortical?

Answer 5

Only the retinoGeniculostriate pathway

Question 6

Which retinal pathway(s) are non-cortical?

Answer 6

The rest: Pretectal, Tectal, and Hypothalamic

Question 7

Which pathway travels via the Lateral Geniculate Nucleus?

Answer 7

Retinogeniculostriate

Question 8

Which pathway travels via the Pretectal nuclei?

Answer 8

Retinopretectal

Question 9

Which pathway travels via the rostral/superior colliculi?

Answer 9

RetinoTECTAL

Question 10

Which pathway travels via the suprachiasmatic nucleus?

Answer 10

RetinoHYPOTHALAMIC

Question 11

Which pathway is associated with:
conscious perception of vision
Menace Response Pathway

Answer 11

Retinogeniculostriate

Question 12

Which pathway is associated with:

PLR (pupillary light reflex)

Answer 12

RetinoPREtectal

Question 13

Which pathway is associated with:

Ocular Fixation Reflex

Answer 13

RetinoTECTAL

Question 14

Which pathway is associated with:

Circadian Rhythms

Answer 14

RetinoHYPOTHALAMIC

Question 15

What % of optic tract axons go to the LGN in the Thalamus?

Answer 15

80%

Question 16

What tests do we use to test for conscious perception of vision (Retinogeniculate Reflex)?

Answer 16

Maze
Cotton Ball
Visual Placement Test: Animal attempts to place paws on table in front of them
Menace Response

Question 17

What % of axons bypass the LGN and synapse onto the Pretectum or Rostral Colliculus?

Answer 17

20%

Question 18

What is the Edinger-Westphal Nucleus?

Answer 18

The parasympathetic nucleus of CN3
Associated with RetinoPREtectal Pathway
Axons synapse here after synapsing onto the pretectum and rostral colliculus

Question 19

What is the result of axons synapsing onto the Edinger-Westphal Nucleus?

Answer 19

Pupil constriction

Question 20

What is Miosis? Which pathway is it associated with?

Answer 20

Pupil constriction- RetinoPREtectal Pathway

Question 21

How do we use a penlight, pupillary light reflex (PLRon) and the RetinoPREtectal Pathway to test for lesions?

Answer 21

You are testing Sensory of CN2 and Motor of CN3

Do a direct test of PLR and an indirect test of PLR on both eyes- OS- left and OD- right

Question 22

What is O.S.?

Answer 22

Left Eye

Question 23

What is O.D.?

Answer 23

Right Eye

Question 24

Where is the lesion located if you get negative PLRs for both direct and indirect tests of the O.S. (left eye), but positive PLRs for the O.D. (right eye)?

Answer 24

Lesion of the optic nerves BEFORE the optic chiasm associated with Sensory CN2

Question 25

If you have a lesion ON the optic chiasm, what would your direct and indirect PLR tests look like?

Answer 25

For O.S. (left eye): Direct and Indirect PLRs both +

For O.D. (right eye): Direct and Indirect PLRs both +

Question 26

If there is a lesion located AFTER the optic chiasm on the RIGHT side, what would your direct and indirect PLR tests look like?

Answer 26

For O.S. (left): Direct and Indirect PLRs both +

For O.D. (right): Direct and Indirect PLRs both +

Question 27

Where could there be a lesion if direct and direct PLR tests of both right and left eyes come up (+)?

Answer 27

AT the optic chiasm or after the optic chiasm

Question 28

What is a common problem seen with brainstem trauma?

Answer 28

PLR abnormalities

Question 29

What is Anisocoria?

Answer 29

Uneven pupil size

Question 30

What is the retinoTECTAL pathway for?

Answer 30

For reflex movements of the eyes and head towards visually interesting stimuli and processing visual info withOUT conscious awareness.

Question 31

What is “blindsight”

Answer 31

The processing of visual info without conscious awareness

Question 32

Describe the pathway of axons of the retinoTECTAL pathway.

Answer 32

Axons–> Rostral Colliculi (in the midbrain)–> MANY PLACES!

CN-3,4,6
Spinal Muscles
Thalamus
Cerebellum

Question 33

The RetinoHYPOTHALAMIC Pathway is especially important in what species?

Answer 33

Sheep and Goats, and HORSES

for reproductive cycles associated with circadian rhythms and photoperiods

Question 34

If there is a loss of PLR…

How can you tell if the problem is due to a CN2 deficit or a CN3 deficit?

Answer 34

Using the INDIRECT test!
If problem in CN2, NEITHER eye has PLR.

If CN3 isn’t working, ONLY the affected eye has no PLR (either direct or indirect).

Question 35

Where in the Vision Pathway would you see partial decussation?

Answer 35

Between the optic chiasm and optic tract AND

Between the Pretectal Nuclei and the EWN

Question 36

If I say “STARTLE REFLEX” you say:

Answer 36

TECTAL pathway!

Question 37

What is Horner’s Syndrome?

Answer 37

Lose innervation to the eye and 3rd eyelid comes up
Due to:
Preganglionic= Disc rupture, neck trauma
Postganglionic= Otitis or Orbital Disease

HAPPENS RANDOMLY- Most common- Idiopathic mean random